The use of various polymers as dye transfer inhibitors (DTIs) in laundry detergent compositions and rinse conditioners has been described in the prior art. Examples of well-known polymers include polyvinyl pyrrolidone (PVP), and copolymers of N-vinylpyrrolidone and N-vinylimidazole (PVP/PVI), available commercially from BASF, Ludwigshafen, Germany as Sokalan (Trade Mark) HPSO and HP56 respectively.
The polymers may be incorporated into particulate detergent compositions directly, for example, as a solution or dispersion, or by dry-mixing powdered polymer with other particulate components. However, the dry-mixing method can lead to deterioration of powder properties, for example, loss of flow and caking, resulting in poor product dispensing into the wash. Powdered polymers can also be difficult to handle.
Alternatively, the polymer may be premixed or granulated with an inert carrier material or another detergent ingredient before incorporation into the detergent composition.
EP 677 580A (Procter & Gamble) discloses a free-flowing powder of high bulk density which contains 5 to 50% by weight of a PVP/PVI polymer and 20 to 95% by weight of a detergent ingredient selected from aluminosilicate, citrate, silica, carbonate, bicarbonate, silicate, sulphate, phosphate, and water-soluble polymers. The preferred and exemplified detergent ingredient is zeolite 4A.
The present invention is concerned with a granular polymer composition containing a different, novel and highly effective dye-transfer-inhibiting polymer. The novel polymer, supplied as an aqueous solution, displays a tendency to discolour on storage; and if spray-dried gives very hygroscopic granules. The granular polymer composition of the invention simultaneously solves the discolouration problem and provides a convenient method for incorporating the polymer into a particulate detergent composition without handling difficulties and without having a detrimental effect on powder properties.